The subject of the invention relates to a method for producing a metallic honeycomb body and to a device for producing a metallic honeycomb body.
For the reduction of pollutants in exhaust gases, in particular in motor vehicle exhaust gases, so-called catalysts are used. The catalysts contain a carrier body which is provided with a catalytically active coating. The carrier body has a multiplicity of ducts through which an exhaust gas is capable of flowing. It has a honeycombed structure, and therefore such carrier bodies are designated as honeycomb bodies.
It is known that such a honeycomb body may be a monolithic body that is produced, for example, from a ceramic material.
Honeycomb bodies are also known which contain a metallic material. Such honeycomb bodies may be produced, for example, by sintering or casting. Metallic honeycomb bodies that contain at least partially structured sheet metal layers are also known.
European Patent EP 0 263 324 B1 describes a metallic honeycomb body which is formed from a corrugated or a smooth and a corrugated metal strip. The metal strip or metal strips are wound or folded to form a plurality of layers contiguous to one another. European Patent EP 0 263 324 B1 shows a spirally wound honeycomb body. The spirally wound honeycomb body is introduced into a casing tube with the aid of an introduction unit.
International Patent Disclosure WO 97/06358 discloses a method for producing a honeycomb body having a multiplicity of ducts permeable to a fluid, from a multiplicity of at least partially structured metal sheets. According to this method, a stack composed of a plurality of at least partially structured metal sheets is disposed in layers. The stack is introduced into an open mold and is held in the latter in a central region by a holding device. At least two mold segments of the mold are in each case displaced out of their initial positions in such a way that at least a portion of each casing section comes to bear on the stack and is subsequently moved along a path of movement corresponding to the outer shape until a predetermined degree of wrap is achieved. The mold is then closed. The matrix thus produced is introduced into a casing tube.
International Patent Disclosure WO 97/06358 describes, furthermore, a method in which a plurality of stacks composed of a plurality of at least partially structured metal sheets are disposed in layers. Each stack is folded in each case about a bending line. The stacks are introduced into an open mold and are held in the latter in a central region by a holding device. At least two mold segments are in each case displaced out of their initial positions in such a way that at least a portion of each casing section comes to bear on the stack and is subsequently moved along a path of movement corresponding to the outer shape until a predetermined degree of wrap is achieved. The mold is then closed. The matrix thus produced is introduced into a casing tube.
International Patent Disclosure WO 97/00135 discloses further methods for producing a honeycomb body, having a multiplicity of ducts permeable to a fluid, from a multiplicity of at least partially structured sheet metal layers. In these methods too, a matrix composed of at least one at least partially structured sheet metal layer, which is wound, layered or wrapped, is formed. The matrix is introduced into a casing tube.
While the matrix is being produced, stresses distributed unevenly over the cross section of the matrix occur and may lead to defects and to dimensional inaccuracies after a soldering operation that follows the production of the honeycomb body. This problem arises to an increased extent when the matrix is formed from sheet metal layers that have a microstructure and a macrostructure, in particular a transverse microstructure.
It is accordingly an object of the invention to provide a method and a device for producing a metallic honeycomb body that overcomes the above-mentioned disadvantages of the prior art methods and devices of this general type, in which an equalization of the stresses over the cross section of a matrix is obtained.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for producing a metallic honeycomb body. The method includes the steps of providing a matrix formed of at least one at least partially structured sheet metal layer being one of wound, layered and wrapped to form the matrix; vibrating the matrix by an external excitation; and introducing the matrix into a casing tube.
In the method according to the invention, the matrix is wound, layered or wrapped from at least one at least partially structured sheet metal layer. The matrix is set in vibration by the external or independent excitation and is introduced into the casing tube during the excitation or after the excitation. Since the matrix is set in vibration by the excitation, an equalization of the stresses in the cross section of the matrix is achieved. This equalization also leads to possible gaps between adjacent sheet metal layers being closed, since, due to the independent excitation of the matrix, an essentially homogeneous relief of stress of the matrix occurs. A more even stress distribution also leads, in the case of a matrix containing smooth and structured sheet metal layers, to the contact forces at the contact points between the smooth and the structured sheet metal layers being distributed more homogeneously, with the result that an improved diffusion connection can be achieved between the sheet metal layers or between the matrix and the casing tube.
It became clear, in particular, that, in the method according to the invention, a more homogeneous stress distribution over the cross section of the matrix can be achieved in the matrix that is formed by sheet metal layers with a microstructure and a macrostructure.
The excitation of the matrix may take place periodically, in a pulse-like manner or randomly in time. It is particularly expedient if the matrix is set in vibration by periodic excitation.
According to a further advantageous refinement of the method, it is proposed that the matrix be set in vibration by kinematic excitation. The advantage of this is that the excitation can be carried out at relatively low outlay. In particular, a kinematic excitation of the matrix has the advantage that relatively low sound emission due to the kinematic excitation occurs.
Alternatively or additionally to a kinematic excitation of the matrix, it is proposed that the matrix be set in vibration by the action of force. The advantage of external excitation by the action of force is that the excitation can be achieved by a relatively high frequency. Furthermore, a predetermined energy can be introduced into the matrix by the action Of force.
According to a further advantageous refinement of the method, it is proposed that the matrix be introduced into the casing tube by the introduction or guide unit, the matrix being compressed and set in vibration during the leadthrough operation. The advantage of this procedure is that the forces necessary for introducing the matrix into the casing tube are reduced. This also results in a reduction in the deformation of the matrix in an end face on which engages a transport element pushing the matrix into the casing tube. This also leads to an improvement in the quality of the honeycomb body.
The excitation of the matrix preferably takes place in such a way that the matrix is set in transverse vibration by the excitation.
According to a further idea of the invention, a device is proposed for producing a metallic honeycomb body which has at least one matrix which is wound, layered or wrapped from at least one at least partially structured sheet metal layer and which is disposed in the casing tube. The device is distinguished by a introduction unit which has an entry orifice and an exit orifice and also a guide duct narrowing from the entry orifice toward the exit orifice. A transport element is capable of being moved in the duct and out of it, the transport element pushing a matrix through the entry orifice into the duct and pressing it via the exit orifice out of the guide unit into a casing tube. The device according to the invention has an exciting unit that is connected to the guide unit and by which the guide unit is set in vibration. The guide unit is set in vibration, in particular, transversely to the axial direction of the duct. When a matrix is located in the guide unit, the matrix is set in vibration via the guide unit, with the result that an essentially homogeneous relief of stress of the matrix is achieved in the guide unit.
To simplify the introduction of the matrix into a casing tube and for positioning the casing tube exactly in relation to the duct, it is proposed that the exit orifice be followed by a positioning unit, by which the casing tube can be positioned essentially coaxially to the duct.
According to a further advantageous refinement of the device, it is proposed that the entry orifice be preceded by a centering unit, so that it becomes simpler for the matrix to be introduced into the duct of the guide unit.
According to a further advantageous refinement of the device, it is proposed that the introduction or guide unit be mounted elastically. An active insulation of the guide unit is achieved by the elastic mounting of the guide unit. By virtue of the active insulation of the vibration unit, no or only very slight vibrational forces pass into the surroundings. External concussions do not reach the guide unit, or only to a very slight extent, so that passive insulation is also afforded.
According to a further advantageous refinement of the device, it is proposed that the exciting unit introduce an oscillating force into the guide unit, the force running essentially transversely to the longitudinal direction of the duct. Alternatively or additionally, the exciting unit may set the guide unit kinematically in vibration transversely to the longitudinal direction of the duct.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and a device for producing a metallic honeycomb body, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.